This invention relates to a voltage testing device for use with an electric tooth-brush having an electric potential generating means.
This type of tooth-brush has been disclosed in U.S. patent application Ser. No. 06/762,976 filed on Aug. 6, 1985 by the present applicant and will be briefly described herein with reference to FIGS. 1 and 2.
In these figures, an electric tooth-brush 21 has a handle 22 including a grip portion 23 in which a battery 24 is accommodated. An electrically conductive bar 25 is embedded in the handle 22, having one end being in contact with a negative pole of the battery 24 and the other end reaching brush bristles 26. Adjacent the brush bristles 26, slots 27 and 28 are formed in top and bottom surfaces of the handle 22, respectively. An electrically conductive cover plate 29 wrapping the grip portion 23 is in contact with a positive pole of the battery 24. A collar 30 is provided for blocking saliva flowing out of the brush bristles which would otherwise reach fingers grasping the grip portion.
During tooth brushing with the tooth-brush 21, the positive pole of the battery 24 electrically conducts to the user's hand through the cover plate 29 and the negative pole to the oral cavity through the electrically conductive bar 25 and saliva in the slot 28, thereby establishing a closed circuit. When a toothpaste containing fluoride is used, this closed circuit causes electrical permeation of fluorine ions into the teeth, thereby ensuring protection and prevention against tooth decay and pyorrhea.
Obviously, the potential of the battery 24 used in the aforementioned electric tooth-brush will decrease as days go by and eventually, the battery will lose requisite energy. Therefore, an instrumental member for measurement of potential of the battery 24 has hitherto been proposed, by means of which an ammeter is provided directly on or in the handle or an indication lamp is attached thereto, and the instrumental member disadvantageously becomes a complicated structure which is disposed of upon disposal of a tooth-brush even if the measuring member is still usable. Inevitably, this tooth-brush with the instrumental member becomes expensive.